Answer:
The velocity of the student has after throwing the book is 0.0345 m/s.
Explanation:
Given that,
Mass of book =1.25 kg
Combined mass = 112 kg
Velocity of book = 3.61 m/s
Angle = 31°
We need to calculate the magnitude of the velocity of the student has after throwing the book
Using conservation of momentum along horizontal direction


Put the value into the formula


Hence, The velocity of the student has after throwing the book is 0.0345 m/s.
If you transfer equal amounts of geat to 1kg of water and 1kg of cooper, the temperature of the cooper will change more . . . it'll get more degrees warmer than the water will.
That's because the specific geat of water is greater than the specific geat of cooper.
(This just means it takes more geat to warm some mass of water by some amount than it takes to warm the same mass of cooper by the same amount.)
Frequency: 
Explanation:
The force experienced by an electron in a magnetic field is

where
is the electron charge
v is the speed of the electron
B is the strength of the magnetic field
Since the force is perpendicular to the direction of motion of the electron, the force acts as centripetal force, so we can write:

where
r is the radius of the orbit
is the mass of the electron
Re-arranging the equation,
(1)
We also know that in a circular motion, the speed is equal to the ratio between circumference of the orbit and orbital period (T):

Substituting into (1),

We also know that 1/T is equal to the frequency f, so

In this problem,

Therefore, the frequency of the electrons is

Answer:
120°
Explanation:
Draw a free body diagram. There are three forces acting on the traffic light. Two tension forces acting along the cables, and weight.
The tension forces have an angle θ between them. That means each tension force forms an angle of θ/2 with respect to the vertical. So the y component of each tension force is:
Ty = T cos (θ/2)
Sum of the forces in the y direction:
∑F = ma
Ty + Ty − W = 0
2 Ty = W
Substituting:
2 T cos (θ/2) = W
If W = T, then:
2 W cos (θ/2) = W
2 cos (θ/2) = 1
cos (θ/2) = 1/2
θ/2 = 60°
θ = 120°
Answer:
5 km/hr because he thinks it moves in the same speed of his...